Predicting the protective humoral response to a SARS-CoV-2 mRNA vaccine

• Published in: Clinical chemistry and laboratory medicine Vol. 59; no. 12; pp. 2010 - 2018
• Main Authors: Meschi, Silvia, Matusali, Giulia, Colavita, Francesca, Lapa, Daniele, Bordi, Licia, Puro, Vincenzo, Leoni, Bruno D., Galli, Claudio, Capobianchi, Maria Rosaria, Castilletti, Concetta
• Format: Journal Article
• Language: English
• Published: Germany De Gruyter 25.11.2021; Walter De Gruyter & Company
• Subjects: Adult; Aged; Antibodies; Antibodies, Neutralizing - blood; Antibodies, Neutralizing - immunology; Antibodies, Viral - blood; Antibodies, Viral - immunology; Antibody response; Area Under Curve; Binding; COVID-19; COVID-19 - immunology; COVID-19 - prevention & control; COVID-19 - virology; COVID-19 Vaccines - administration & dosage; COVID-19 Vaccines - immunology; Female; Health care; Health Personnel; Humans; Immune response (humoral); Immunity, Humoral; Immunoglobulin G; Logistic Models; Male; Medical personnel; Middle Aged; mRNA; mRNA Vaccines; Neutralization Tests; protective immunity; ROC Curve; SARS-CoV-2; SARS-CoV-2 - isolation & purification; SARS-CoV-2 - metabolism; Severe acute respiratory syndrome; Severe acute respiratory syndrome coronavirus 2; Spike Glycoprotein, Coronavirus - chemistry; Spike Glycoprotein, Coronavirus - immunology; vaccine; Vaccines; Vaccines, Synthetic - administration & dosage; Vaccines, Synthetic - immunology; viral neutralization; Viruses; Young Adult; SARS-CoV-2; vaccine; viral neutralization; antibody response; protective immunity
• ISSN: 1434-6621; 1437-4331; 1437-4331
• DOI: 10.1515/cclm-2021-0700

Simple and standardized methods to establish correlates to vaccine-elicited SARS-CoV-2 protection are needed. An observational study on antibody response to a mRNA vaccine (Comirnaty) was performed on health care workers (V, n=120). Recovered COVID-19 patients (N, n=94) were used for comparison. Antibody response was evaluated by a quantitative anti-receptor binding domain IgG (anti-RBD) commercial assay and by virus microneutralization test (MNT), in order to establish a threshold of anti-RBD binding antibody units (BAU) able to predict a robust (≥1:80) MNT titer. Significant correlation between BAU and MNT titers was found in both V and N, being stronger in V (rs=0.91 and 0.57 respectively, p<0.001); a higher incremental trend starting from MNT titer 1:80 was observed in the V group. The 99% probability of high MNT titer (≥1:80) was reached at 1,814 and 3,564 BAU/mL, and the area under the receiver operating characteristic (ROC) curve was 0.99 (CI: 0.99-1.00) and 0.78 (CI: 0.67-0.86) in V and N, respectively. A threshold of 2,000 BAU/mL is highly predictive of strong MNT response in vaccinated individuals and may represent a good surrogate marker of protective response. It remains to be established whether the present results can be extended to BAU titers obtained with other assays.